Tectonics of the Afar Depression: A review and synthesis

Beyene, Alebachew; Abdelsalam, Mohamed G.

doi:10.1016/j.jafrearsci.2005.03.003

Cited by 132 publications

(106 citation statements)

References 77 publications

(205 reference statements)

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“…Afar marks a triple junction between the Nubian, Somalian, and Arabian plates, which are diverging due to extension in the Red Sea, Gulf of Aden and East African rifts (e.g., Beyene and Abdelsalam, 2005;Ghebreab, 1998;McKenzie et al, 1970;Mohr, 1970; (Fig. 1).…”

Section: Rift Initiationmentioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The rifting of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental rifting to incipient seafloor spreading. We review recent constraints on along-axis variations in rift morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea rift of Afar to understand processes ultimately responsible for the formation of magmatic rifted continental margins. Our synthesis shows that there is a fundamental change in rift morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower rift. Thus, although magma intrusion accommodates strain for a protracted period during rift development, the final stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic rifted margins worldwide.

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Section: Rift Initiationmentioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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“…Thus, Quaternary rift basins and magmatic segments ( Fig. 1), which display right-stepping lateral offset-tectonics (Wolfenden et al, 2004;Kidane et al, 2006), formed within Miocene rift basins (Beyene and Abdelsalam, 2005). The lithologic and __________________ tectonic features of the herein described Mt.…”

Section: Introductionmentioning

confidence: 76%

“…Beyene and Abdelsalam, 2005;Buck, 2006). Both are composed of continental flood basalts of a related magmatism predating continental break-up by several million years (Ayalew et al, 2006).…”

Section: Geological Settingmentioning

confidence: 99%

“…According to the stratigraphic concept of the Afar region by Varet (1978) and Beyene and Abdelsalam (2005), there exist ENE-trending, around 4 Ma old volcanic centres, that are intercalated with the "Afar Stratoid Series". Some of these comprise trachytic and rhyolitic sequences, referred to as silicic centres Varet, 1975, 1977;Varet, 1978), whose impact was dominant in our research area.…”

Section: _____________________________________mentioning

confidence: 99%

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Paleomagnetic constraints on stratigraphy and rift-related tectonics of Pliocene and Early Pleistocene volcano-sedimentary strata: the Mt. Galili hominid research area, Southern Afar Depression, Ethiopia

Popp¹,

Scholger²

2018

AJES

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Our paleomagnetic investigations in the Northern Main Ethiopian Rift concentrated on ascertaining characteristic remanence directions of volcanic and sedimentary layers embodied within the Mt.Galili Formation (MGF). Magnetic stratigraphy was applied mainly to support anthropological studies on early hominid evolution. The new paleomagnetic results provided implications for stratigraphic age determinations of the MGF, and they also support arguments for rift-related tectonics as block rotation and tilting relative to the stable African crust since the Pliocene.Based on 497 paleomagnetic samples, we applied magnetic stratigraphy on magmatic and sedimentary rocks to determine the 39age of the MGF and correlated the results with published Ar/ Ar age data on tuff and ignimbrite layers which range from ca. 5.4 Ma to ca. 2.3 Ma, consistent with biostratigraphic age constraints. Nine magnetic polarity intervals of the Gilbert zone were identified within the lower four members of the MGF covering a time span from 5.37 to 3.58 Ma. The upper two members of the MGF comprised three polarity intervals assigned to the upper Gauss and lower Matuyama polarity zones. In combination with an 39Ar/ Ar age of 2.35 Ma, located in the middle of the section, we infer that ca. 0.5 Ma and four polarity intervals are missing between the MGF's lower and upper members. We attribute this significant depositional gap to uplift of the region due to the intrusion of basalt magma, associated with deposition of the Upper Shabeley Laag Member.Extensional rift tectonic processes were intimately affiliated with magmatic activity and generation of rapidly changing sedimentary environments of the MGF`s deposits, but the bulk of the observed tectonic features resulted from post-depositional tectonic overprint, when the re-orientated Wonji Fault System affected the Mt.Galili area in the Quaternary period, thereby creating new internal rift (in older rift) structures. Tectonic movements of MGF`s strata were deduced from our analysed characteristic remanent magnetisation (ChRM) directions compared with Pliocene reference data. The investigation revealed almost unchanged orientation of the ChRM-directions for the marginal internal rift zone in the East of the Mt.Galili area, but moderate counterclockwise rotation for the central internal rift zone in the West. The North of the Mt.Galili area suffered moderate clockwise rotation, probably due to the Mt.Galili area`s regional position, adjoining a transfer zone between the Quaternary Angele and Addo-Do magmatic segments.

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“…The Neoproterozoic basement, which represents part of the Arabian-Nubian Shield, is prevalent on the periphery of the Afar Depression. The Arabian-Nubian Shield covers vast terrain to the north and northwest of the Afar Depression and in eastern Eritrea (Beyene and Abdelsalam, 2005 and references therein).…”

Section: Tectonic Settingmentioning

confidence: 99%

A preliminary Geological and Generalized Stratigraphy of Western Margin of Northern Afar Depression, Dallol Area, Northern Ethiopia

Hagos¹,

Konka²,

Ahmed³

2016

mejs

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The western margin of northern Afar Depression constitutes various rock units of Neoproterozoic basement complex, Paleozoic to Mesozoic sedimentary successions and the Oligocene to present volcano-sedimentary sequences. As part of a reconnaissance survey for mineral resources in selected districts of Afar region, a geological and structural map of Dallol area has been produced with the help of the Landsat Thematic Mapper Plus imagery at a scale of 1:100,000 and a simplified stratigraphy is constructed for the western rift margin, Dallol area.

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Tectonics of the Afar Depression: A review and synthesis

Cited by 132 publications

References 77 publications

The development of extension and magmatism in the Red Sea rift of Afar

The development of extension and magmatism in the Red Sea rift of Afar

Paleomagnetic constraints on stratigraphy and rift-related tectonics of Pliocene and Early Pleistocene volcano-sedimentary strata: the Mt. Galili hominid research area, Southern Afar Depression, Ethiopia

A preliminary Geological and Generalized Stratigraphy of Western Margin of Northern Afar Depression, Dallol Area, Northern Ethiopia

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